Bleach Accelerator Releasing Compounds (BAR's) are known for use in color negative photographic elements to aid in the oxidation of silver in photographic systems, so that the resulting silver halide can be effectively removed from the element. The BAR is generally coated in the imaging layers of the film, and the accelerator fragment is either released directly from the compound upon reaction with oxidized developer, or is released from a linking group (which can include timing groups) which itself is released from the compound after reaction with oxidized developer.
In color negative systems the foregoing imagewise release of a bleach accelerator fragment is suitable to aid oxidation of the metallic silver which is also generated imagewise in the element. However, reversal films are first processed by contact with a non-chromogenic developer (that is, a developer which does not cause the formation of colored dyes) to develop exposed silver halide, followed by a fogging treatment of remaining silver halide, followed by treatment with a color developer. Thus, in reversal films, unlike color negative films, silver is generated throughout the image in both regions of maximum image dye density ("dye Dmax") and regions of minimum image dye density ("dye Dmin"). When a BAR is placed directly in an imaging layer or in a non-silver containing interlayer of a reversal film, bleach acceleration in the low exposure regions (dye Dmax regions) is aided, while bleaching remains slow in the high exposure regions (dye Dmin regions). As already discussed, this situation is unsatisfactory in that in a color reversal element silver should be bleached fairly consistently throughout the element. Retained silver in the Dmin regions is particularly objectionable for reversal elements. Sensitometry and image structure a can also be adversely affected by the presence of a BAR in the imaging layers.
It would be desirable then, to have a color reversal element with a BAR which can uniformly assist in silver bleaching throughout the element.